I'm still kinda bitter about this. If Star already loved Marco than why did she waste her time with Tom? And if Marco already had feelings for Star "from the start" than why did he freak after Song Day?
Short answer: they were both young cowardly idiots with very little love experience, confused feelings, and a crippling fear of ruining their friendship by changing things, wallowing in their status quo every time until events finally pushed them to actually look at what they wanted.
Slightly longer answer but still a very short one: Marco knew that Star was special for him since the beginning (well, since some hours after the beginning, technically), but that didnât immediately equal âloveâ, as he himself says. It was a strong bond of friendship that grew and evolved over time.Â
It wasnât until Jackie broke up with him and he moved to Mewni that he finally started to realize that he wanted more from their relationship, and that he wasnât content with the goals he had set for himself since childhood anymore (i.e. date Jackie, have an easy Earth life, and thatâs also why he freaked out after Song Day and never really acknowledged Starâs confession: he didnât know what to do when the way he envisioned his life until that moment was suddenly and explosively challenged), and by then Star was already dating Tom, and even after Booth Buddies and up to a couple of seconds before The Kiss he was still worried about Star not fully reciprocating his feelings, or not being ready for things to change. A classic case of â-but what if dating ruins our friendship?!â.Â
As for Star, after Starcrushed and the beginning of S3 she was heartbroken, unsure if Marco would have ever been a constant or at least frequent part of her life anymore, at a point of change in her life (she wanted to change her ways of being a princess and do something concrete for Mewni), and still had unresolved issues with Tom (sure she was crushing on Marco at the time, but it was too early to talk about the fully conscious love we see in the last episodes of the series). At the time Tom was the perfect (or more like best option) bandage for the Marco shaped hole in her life... or at least she thought until Marco actually came back, and soon enough she immediately started relying on him for everything except for what strictly pertained âdatingâ. Marco grows by helping Star, Star can grow when Marco supports her, allowing her to better deal with whatever The Plotâą threw at her. Or, as Star herself put in her diary (from the Book of Spells),
Thatâs part of the reason behind her relationship with Tom never really evolving: she saw him as a boyfriend, and nothing more. Just someone to occasionally kiss and go on dates with: as soon as her life became less hectic for the first time since Bonbon The Birthday Clown, so after Cornonation, and as soon as Tom pushed for their relationship to somewhat evolve, bam, Doop-Doop happened and that lead to a breakup leading to all the parts involved being forced to accept what they really wanted leading to Starco.
Obviously things get more complex if one wants to analyze the writing and pacing of the show as a whole, since Tomstar was clearly running on heavily borrowed time after the end of S3 and didnât need to last that long and yada yada, but from a strictly in universe and personalities / arcs point of view, Star was essentially scared of the unknown, and having a shallow relationship with Tom, plus the whole Blood Moon bullcrap, was enough to distract her from her real feelings for Marco, and - thatâs what she thought more or less unconsciously obviously things eventually changed since it was an unsustainable situation - a better alternative to taking the plunge and changing the few stable things left in her life: Marco being her best friend partner squire knight emotional and practical support source of happiness, and Tom being her boyfriend. But then as I said Cornonation happened, Star had to rethink her life and goals, and while the last push was given by Tom and other events, things changed and she finally manage to realize (or more like âacceptâ, since the realizations were all there already, just hidden and covered by denial) what she truly yearned for.
More or less the same goes for Marco, who was slightly ahead of Star as far as giving a hard look at his goals for life goes (after The Knight Shift, that is), but so much more unsure and cautious than her as a person, and thus worried about messing everything up until the last moment.
Star managed to convince him otherwise.
